Musk then tweeted an apology: "My words were spoken in anger after Mr Unsworth said several untruths & suggested I engage in a sexual act with the minisub, which had been built as an act of kindness & according to specifications from the dive team leader.

"Nonetheless, his actions against me do not justify my actions against him, and for that I apologise to Mr. Unsworth and to the companies I represent as leader. The fault is mine and mine alone."

But Musk has taken to Twitter again, this time to question why Mr Unsworth hasn't sued him in wake of the remarks.

In a tense Twitter exchange with a journalist Musk added: "Did you investigate at all? I'm guessing answer is no. Why?"

Shares in his company dived by around A$3.5bn following his initial comments, which he now admits were made "in anger".

Last month Mr Unsworth said: "I've been approached by British lawyers, American lawyers. I haven't decided what to do next yet."

"I can't let it go. There's too much out there already," Unsworth told Reuters in an interview.

Asked why he thought Musk would make such a comment about him, he said: "I don't know."

This article first appeared in The Sun and is republished with permission.